Double strike and emphasize are believed to be supported in existing printers by defining the bit map of each character as the overlay of the bit map image of the standard character and that bit map image offset from the first image. For double strike the second image is shifted vertically, and for emphasize the shift of the second image is horizontal. For combined double strike and emphasize the character image bit map is the result of the standard image and the two shifted images as shifted for double strike and emphasize. When the image is printed, a single dot or pel (a standard term believed derived from the phrase "picture element") is printed once at each bit position in which one of the bit maps as so combined defines a dot to be printed.
Typically, the shift of the bit maps for double strike and for emphasize is two pel positions, and the final bit map is obtained from that of the standard character by a digital data processor employing an algorithm to determine the result of such shifting. In accordance with this invention the expanded characters are obtained by an algorithm, but the offsets are not necessarily just horizontal or just vertical or just their direct combination. This is achieved by including modification information in the data stored for each standard font. The expansion of characters is then defined for each character of each font by the modification information of that font, which will be different for fonts having different visual characteristics.
U.S. Pat. No. 3,896,424 to Williams discloses a display apparatus of the video type in which a preceding code character defines the attributes of the display of characters following that code. At column 7 several attributes called out by the code, such as strike out, underline, and double wide, are discussed. An attribute unique to the type style is not suggested.
IBM Technical Disclosure Bulletin article entitled "Energy Management for an Electronic Font Used in a Resistive Ribbon Printer, " Vol. 30, No. 5, October 1987 at pp. 254-255 is illustrative of known prior art in which a code is associated with each character defining the bit density of the character, to which a thermal printer reacts by changing the heat applied to the bits of each character as the character is printed.